The present invention relates to the use of specific tetrahydrobenzoxazines as stabilizers for stabilizing inanimate organic material against the action of light, oxygen and heat, especially in turbine fuels (jet fuels). The present invention further relates to a turbine fuel composition and to an additive concentrate for turbine fuels which comprise these tetrahydrobenzoxazines. The present invention further relates to a process for preparing these tetrahydrobenzoxazines. Since some of these tetrahydrobenzoxazines are novel substances, the present invention also relates to these novel substances themselves.
The mechanical, chemical and/or esthetic properties of inanimate organic material, for example of plastics and coatings, but also of mineral oil products and fuels, are known to be impaired by the action of light, oxygen and heat. This impairment is exhibited typically in the form of yellowing, discoloration, crack formation or embrittlement of the material. Stabilizers or stabilizer compositions with which improved protection against such impairment of organic material by light, oxygen and heat can be achieved are already known.
For instance, WO 05/073152 (1) describes 2-alkylpolyisobutenylphenols and their Mannich adducts as antioxidants for stabilizing inanimate organic material against the action of light, oxygen and heat. Other materials to be stabilized include fuels such as gasoline fuels, diesel fuels and turbine fuels, and also lubricant compositions. In turbine fuels, these 2-alkylpolyisobutenylphenols and their Mannich adducts bring about an improvement in the thermal stability and a reduction in the deposits in the fuel circuit and combustion system of the turbines.
WO 03/106595 (2) also discloses, as well as hydrocarbyl-substituted succinic acid derivatives and polyalkenylthiophosphonate esters, Mannich adducts made from hydrocarbyl-substituted phenols, an aldehyde and an amine as additives for turbine fuels (jet fuels) for improving the thermal stability and for reducing deposits.
However, especially for the mineral oil product and fuel sector, there is a need for stabilizers and antioxidants with improved protective action against the impairment of the material properties by light, oxygen and heat. For turbine fuels (jet fuels) in particular, which are exposed to extreme thermal stress during and before the combustion operation in turbines, for example in aviation turbines, novel improved stabilizers are being sought. In the turbines, these should simultaneously also reduce deposits in the fuel circuit and in the combustion system by virtue of their mode of action as antioxidants and/or dispersants.
It was therefore an object of the invention to provide stabilizers with an improved stabilization of inanimate organic material, especially of mineral oil products and fuels, in particular of turbine fuel, against the action of light, oxygen and heat.